Optimization of AAV tools to target Müller glial cells for retinal gene therapy.

Reprogramming of Müller glial (MG) cells into retinal neurons has the potential to treat vision loss by regenerating the retina. Development of efficient gene delivery systems to target the MG cells is critical for this approach. Adeno-associated virus (AAV) serotypes and promoter specificity are important factors that influence AAV transduction profile in the retina. However, studies optimizing these parameters to specifically target MG cells are limited, particularly in rats which are widely used for eye research. In this study, we tested 4 AAV serotypes and 13 promoters to optimize gene delivery to human MG cells in vitro and/or rat MG cells in vivo. We showed that the combinatorial use of MG-specific serotypes and promoters achieved high specificity for MG cell targeting, with ShH10Y serotype and the GFAP (gfaABC1D) promoter as the best performing tool to target rat MG cells in vivo. We developed AAV vectors using known and novel MG-specific promoters and engineered short promoter variants to improve the cargo capacity of AAV delivery. Our results highlighted a panel of promoters that can target MG cells in vitro or in vivo. This study further expands the AAV toolbox for MG-targeted gene delivery, which has important implications for retinal gene therapy.